Synthesis of Ordered, Phase-Separated, Organic and Metal-Containing Ionic Liquid-Based Block Copolymers via Controlled Radical Polymerization

Polymerized ionic liquids (PILs) are a class of polyelectrolytes that contain an ionic liquid (IL) moiety in each monomer repeating unit that are connected through a polymeric backbone. Since ILs are small-molecule liquid materials with a unique combination of properties (e.g., negligible vapor pressure, high thermal stability, ion conductivity, high solubility for certain light gases, etc.), the development of ordered, phase-separated polymeric systems containing PIL segments has considerable implications with respect to a range of transport-dependent, energy-based technology applications. The work presented in this thesis was focused on the synthesis of two IL-based block copolymer (BCPs) platforms: (1) a new organic IL-based BCP platform (PIL-BCP) and its morphological phase behavior; and (2) the first example of metal-containing IL-based BCP (MCIL-BCP) platform that forms ordered microstructures in the neat state and has functional capabilities introduced by the incorporated metal complex. The PIL-BCP platform was synthesized via sequential atom-transfer radical polymerization (ATRP) of styrene and styrenic imidazolium IL monomers with different side-chains on the imidazolium units (e.g., methyl, n-butyl, etc.). Small-angle X-ray scattering (SAXS) analysis of these BCPs showed the formation of four classic ordered morphologies of diblock copolymer (i.e., body-centered cubic spheres (SBCC), hexagonally packed cylinders (Hex), lamellae (Lam), and notably, bicontinuous gyroid (Gyr)), depending on both the volume fraction of the PIL block and the attached alkyl group on the imidazolium units. The MCIL-BCP platform was synthesized by sequential reversible addition-fragmentation chain transfer (RAFT) polymerization of butyl methacrylate and a Co(II) bis(salicylate) anion-containing MCIL monomer. SAXS studies on MCIL-BCP samples made from these two monomers with 70 total repeat units but different block composition ratios showed the formation of ordered microstructures (i.e., S, Hex, Lam, and Gyr phases) in their neat states. This is the first example of an IL-based BCP that exhibits the Gyr phase in the neat state to our knowledge. Additionally, these MCIL-BCPs were found to have metal-induced properties such as reversible binding of small protic molecules and catalytic reactivities.</p

Asymmetric reflection induced in reciprocal hyperbolic materials

Reflection is one of the most fundamental properties of light propagation. The ability to engineer this property can be a powerful tool when constructing a variety of now ubiquitous optical and electronic devices, including one-way mirrors and antennas. Here, we show from both experimental and theoretical evidence that highly asymmetric reflection can be induced in reciprocal hyperbolic materials. This asymmetry stems from the asymmetric cross-polarization conversion between two linearly polarized waves, an intrinsic and more exotic property of hyperbolic media that is bereft of research. In addition to angle-controllable reflection, our findings suggest that optical devices could utilize the polarization of the incident beam, or even the polarization of the output wave, to engineer functionality; additionally, in hyperbolic slabs or films, the asymmetry can be tailored by controlling the thickness of the material. Such phenomena are key for directional-dependent optical and optoelectronic devices

High-power continuous-wave optical waveguiding in a silica micro/nanofibre

We demonstrate CW optical waveguiding in a silica MNF with power up to 13 W, making it possible for high-speed optomechanical driving of microparticles, and efficient second/third harmonic generation